OBJECTIVE: The purposes of this study were to observe the radiographic changes of lumbar facet joints by magnetic resonance imaging (MRI) in conservatively and operatively treated groups of patients with herniated intervertebral disc, and to compare the biomechanical effects to lumbar facet joints according to the treatment methods. METHOD: The patients composed of 20 conservatively treated control group and 40 operatively treated group who had disc herniation at lower lumbar spine. Follow-up MRIs were performed in order to assess the radiographic changes of intervertebral disc and lumbar facet joints, such as disc degeneration, lumbar facet joint angle and tropism in either treatment groups individually. RESULTS: There are significant increase in lumbar facet joint angle in operatvely treated group at the level of both L4/5, right L5/S1 compared to that of conservately treated group, but the disc degeneration and facet joint tropism were not changed after treatment in both groups. There's no relationship between treatment period and each parameters. CONCLUSION: The radiographic biomechanical lumbar facet joint changes on MRI seems to be related to degenerative change of lumbar facet joint in operatively treated group with a lumbar disc herniation. Therefore, careful selection of optimal operation time and criteria would be important.